Pelagic food web interactions among benthic invertebrates and trout in mountain lakes

Abstract

1. Benthic chironomid larvae and the amphipod Gammarus lacustris have been observed in the pelagic habitats of many mountain lakes. The main goal of this study was to determine if chironomid larvae and gammarids potentially affect predator-prey and nutrient dynamics in pelagic food webs of mountain lakes. 2. Eighty-six mountain lakes were surveyed in Alberta and eastern British Columbia during the years 1965-1984, 1991-2004 and 2005-2007. Pelagic chironomid larvae were found in 86% of these lakes, and pelagic gammarids were found in 29% of lakes. Densities of pelagic chironomid larvae were 92% lower in lakes with pelagic gammarids and 76% lower in lakes with trout (P < 0.05). Intraguild predation of trout on gammarids appeared to reduce predation pressure on chironomid larvae. Gammarids consumed in vitro about 1 chironomid per gammarid per day or about 20% of their body mass in chironomid biomass per day. 3. Concentrations of total dissolved P and N, particulate C, and chlorophyll-a increased with increasing densities of pelagic gammarids and chironomid larvae in situ (R 2 = 0.14 ± 0.19 SD, P < 0.1) and in vitro (P < 0.001). 4. Our findings suggest that gammarids and chironomid larvae are linked as predators and prey in pelagic food webs, possibly stimulating phytoplankton abundance via nutrient release.

Invasive crayfish increase habitat connectivity: a case study in a large boreal lake

“…In general, macroinvertebrates have an important role in energy and nutrient cycling in freshwater ecosystems (Covich et al, 1999). For example, migration of these animals between benthic and pelagic habitats and the physical perturbation of substrates could enhance benthic-pelagic linkage via increase in nutrient release (Vanni, 2002;Weidman et al, 2011). We suggest that expansion of this largebodied invader to the deep water areas potentially alters in several ways these habitats where physical conditions are presumably rather stable and natural perturbation is low (Stendera and Johnson, 2008).…”

Freshwater food webs: towards a more fundamental understanding of biodiversity and community dynamics

“…Replicated experimental manipulations in food‐web ecology are still far less common than correlational gradient–based studies, yet they are essential if we are to use network‐based approaches to assess the impacts of environmental change as a dynamic stressor. As such, they can complement gradient‐based approaches, as illustrated in a recent study of pelagic food webs that used complementary experimentation to determine the processes underlying patterns observed in natural lakes (Weidman, Schindler & Vinebrooke, 2011). Of course, for experimentation, context is important, and we should remember that if the stressor is both large enough and fast enough, new equilibrium conditions might never be reached.…”

“…Food‐web studies are now explicitly incorporating biological mechanisms from behaviour (Meerhoff et al. , 2007; Weidman et al. , 2011), functional traits (Costantini & Rossi, 2010) and ecosystem energy fluxes (Kawaguchi & Nakano, 2001).…”

“…Global coverage of detailed freshwater food‐web studies now extends from grassland streams in New Zealand (Townsend et al. , 1998) to alpine lakes in North America (Weidman et al. , 2011), and encompasses Brazilian reservoirs (Okun et al.…”

Interactive effects of higher temperature and dissolved organic carbon on planktonic communities in fishless mountain lakes

“…High zooplankton densities in small mesocosms are likely to have intensified nutrient recycling, competition and predation pressure (Wilhelm, Schindler & McNaught, 2000;Weidman et al, 2011). High zooplankton densities in small mesocosms are likely to have intensified nutrient recycling, competition and predation pressure (Wilhelm, Schindler & McNaught, 2000;Weidman et al, 2011).…”